4i8 



The Plane Tree Family 



leaves being killed in May or June by the minute fungus Glocosporium nervi- 

 sequiim Saccardo, though the second crop of leaves clothes the branches in July. 

 The European species, P. oricntalis Linnaeus, is less subject to this disease. 



2. ARIZONA SYCAMORE - Platanus Wrightii S. Watson 



This tree is also called the Arizona plane tree, but locally simply Sycamore. 

 It is known only from the mountain canons of southwestern New ^Mexico, south- 

 ern Arizona and Sonora, at eleva- 

 tions of about ^800 meters. Its 

 greatest height is 24 meters, with a 

 tnmk diameter of 1.5 meters. 



It much resembles the above de- 

 scribed tree in bark and manner of 

 branching. The twigs are slender, 

 thickly woolly at first, but soon be- 

 come smooth and light reddish 

 brown or gray brown in color; the 

 winter buds are conic, sharp-pointed, 

 about 5 mm. long. The leaves are 

 15 to 20 cm. across, lobed to below 

 the middle into 3 to 7 elongated 

 wedge-shaped, sharp- pointed, or 

 Fig. 366. -Arizona Sycamore. ^^^.^j^ rounded lobes, which are en- 



tire or toothed; the base is usually heart-shaped, seldom truncate or wedge-shaped; 

 they are thin, firm, hght green, and smooth above, pale and hairy beneath; the 

 stout, usually smooth leaf-stalk is 3 to 5 cm. long; the stipules are small, seldom 

 over 10 mm. long, and usually entire. The flowering peduncles are covered with 

 thick, whitish hairs. The fruit heads, of which there are from 2 to 5, are 2 to 3 

 cm. in diameter, and hang on a smooth, slender stem, 15 to 20 cm. long; the 

 lateral heads are on stalks 2 to 2.5 cm. long. The nutlets are smooth, angular, 

 about 6 mm. long, rounded at the top and capped by the short, curved, persistent 

 style. 



The wood is ven,- similar to that of the previously described tree, except 

 that it is considerably Hghter in weight, its specific gravity being about 0.47. 



3. CALIFORNIA SYCAMORE - Platanus racemosa Nuttall 



Also known as the CaHfomia plane tree. Button ball, and Button -ball tree, 

 occurs from Alameda county, California to the mountains of Lower Cahfomia, 

 growing along the water courses, up to an elevation of 900 meters. Its maximum 

 height is about 38 meters, with a trunk diameter of 2.7 meters. 



In trunk, bark, and manner of branching it is similar to the other American 



